US2166396A - Piano action - Google Patents

Description

July 18, 1939. c. H. DAsENBRooK PIANO ACTION Filed March 6, 1937 NVENTOQ,

Patented July 18, 1939 PATENT OFFICE PIAN Charles H. Dasenbrook,

ACTION Rockford, Ill., assigner to Thayer Action Company, Rockford, Ill., a

corporation of Illinois Application March 6, 1937, Serial No. 129,306

3 Claims.

This invention relates to piano actions and the general object is to provide a connection of novel construction for transmitting the motion from the rear end of each key to the action proper in a novel manner such as to minimize frictional Wear between the contacting parts and avoid the necessity of accurate location of the pivot centers and points of contact.

A more detailed object is to provide a motion transmitting connection of the above character which is especially adapted for use in a piano action of the general type disclosed in my Patent No. 2,073,463. v Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawing, in which Figure l is a vertical cross sectional view of a piano action embodying the novel features of the present invention.

Fig. 2 is an enlarged fragmentary view of the improved motion transmitting connections showing the parts in different positions.

For purposes of illustration, the invention is 25 shown in the drawing as embodied in an action for a piano of the so-called upright or vertical grand type having hammers 5 which are projected against vertically disposed strings 6 in response to depression of corresponding keys 1. 30 In accordance with standard practice, the keys are fulcrumed at 8 on a balance rail 9 supported by a bed I0.

The action propel' and the mechanism for transmitting the motion of the keys to the action are mounted on a common frame or bracket l! supporting a main rail I2 on which the hammers 5 are pivoted. The butt of the hammer carries a leather surfaced knuckle i3 which is engaged eccentrically of the hammer pivot by the end of a jack I4 pivoted at l5 on a whip I6. The latter is disposed in a generally horizontal position and is supported at its rear end from a ange on the rail I2 so as to swing about a xed pivot I1.

As the whip l5 is swung upwardly from the idle position shown, the jack is raised thereby projecting the hammer forwardly until an arm I8 on the jack strikes a regulating button I9 as the hammer approaches the string. The whip carries the usual back check 20 which coacts in a well known manner with a catcher carried by the hammer butt. The action also includes the usual string damper 22 on the upper end of a lever 23 which operates in a well known manner in conjunction with a spoon 24 upstanding from the rear end of the whip.

While in some instances, the key motion may be transmitted directly to the lever I6 or whip, this is effected herein through the medium of a connection for each key including a vertically extending link 25 pivotally connected at its lower end to the forward end of the Whip i6 and at its upper end to the rear end of a lever 26 which projects over the rear end of the key and is supported at its forward end to turn about a Xed pivot 21 on a rail 28 carried by the action frame II. To permit adjustment of the length of the connections, each includes an upright capstan screw 29 threaded into the rear end of the key and having an upper surface 30 on its head bearing upwardly against a downwardly facing surface 3| formed by a pad 32 of fabric or other similar material fastened to the underside of the lever 26. The point of engagement between the lever 26 and the screw is so positioned relative to the key and lever fulcrums as to provide for transmission of the key movements to the jack with the proper mechanical advantage.

Owing to the substantial distance between the key and lever fulcrums 8 and 21, the points on the screw surface 313 and the pad surface 3| which contact each other in the released position of the key as shown in Fig. 1 will move in different arcs 33 and 34 as the key is swung through its range of movement. As a result, some relative rubbing movement occurs between the engaging surfaces of the pad and screw in actions as generallyvconstructed. Such rubbing movement, if of any substantial magnitude, is detrimental not only because of the resulting wear but also because it impairs the so-called touch of the piano action. The degree of such rubbing may be reduced to some extent by the accurate location of the lever fulcrum 21 on a line 35 through the fulcrum 8 and the initial point of contact between the screw and pad surfaces 30 and 3|. Sufciently accurate location of the fulcrum 21 is seldom obtainable in practice, and the tendency in assembling the actions is to insure location of the fulcrum on the side of the line 35 which i`s less detrimental, that is, below this line in pianos of the type illustrated.

The present invention contemplates a special shaping of the engaging surfaces 3G and 3| so as to insure substantial elimination of rubbing between these surfaces even though the fulcrum 21 is not located accurately. To this end, the convex surface 30 of the capstan screw is formed with a substantially shorter radius of curvature than in adjusting screws heretofore employed,

and the pad surface 3| is of non-convex curvature preferably being substantially flat as shown. a depressible key fulcrumed intermediate its ends, with the actuated lever 25 disposed as shown, the point of contact 3B between the surfaces in the idle position of the parts as shown in full lines in Fig. 2 will be disposed to the right of the screw axis. As the key is depressed, the surfaces 3G and 3l will roll relative to each other without appreciable 4relative movement between the engagng points and with the point of contact between the two substantially coinciding with the arc 34. Thus, in the eXtreme actuated position of the key, the screw and pad surfaces will engage at the point 3l as shown in dotted outline in Fig. 2. In this way, relative movement between the engaging points of the screw and lever surfaces is effectually minimized thereby eliminating objectionable frictional wear on the pad and at the same time preserving the desired key touch.

I claim as my invention:

1. In a piano construction, the combination of a depressible key fulcrumed intermediate its ends, a capstan screw upstanding from the rear end portion of said key and having an upwardly facing convex head surface, a lever above the rear end of said key inclined relative thereto upwardly and rearwardly in the released position of the key and having a downwardly facing surface intermediate its ends engaging said head surface, said levor being fulcrumed at one end to swing about a pivot offset slightly in a direction opposite that of the capstan screw movement from a line extending between said key fulcrum and the normal point of contact between said lever surface and said head surface, and an action unit actuated from the opposite end of said lever, said lever having a substantially fiat surface engaging said convex surface and cooperating therewith to provide true rolling contact therebetween throughout the range of movement of said key.

2. In a piano construction. the combination of a depressible key fulcrumed intermediate its ends, a capstan screw upstanding from the rear end portion of said key and having an upwardly facing convex head surface, a lever fulcrumed at one end on a pivot spaced from said key fulcrurn and having a substantially iiat bearing surface contacting said head surface, said pivot being disposed substantially on a line extending through the key fulcrum and the point of engagement between said screw and fiat surface when the key is in released position, and an action unit actuated by said lever.

3. In a piano construction, the combination of a depressible key fulcrumed intermediate its ends, a capstan screw upstanding from the rear end of said key and having anv upwardly facing surface, a lever fulcrumed at one end on a pivot spaced from said key fulcrum and having a downwardly facing surface contacting said screw surface, said pivot being disposed substantially on a line eX- tending through the key fulcrum and the point of engagement between said screw and lever surfaces when the key is released, and an action unit actuated by said lever, one of said surfaces being of convex curvature and the other being substantially fiat whereby to provide for rolling contact between the surfaces during the range of movement of the key and thereby substantially eliminating rubbing friction between the surfaces.

CHARLES H. DASENBROOK.

CERTIFICATE "0F coRlrEoTloN,` Patent No. 2,166,596. July 18, 1959.

' CHARLES H. DASENBROOK.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, first column, line 5, strike out the words and comme "a depressible key fulorumed intermediate its ends," and insert instead with the surfaces 50 and 51 so shaped and; and that the said Letters Patent shouldbe readwith, this oor-f rection therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 5th day of September, A. D. 1959.

Henry Van Arsdale,

(Seal) y A Acting Commissioner of Patents.

CERTIFICATE CF CORRECTION.. Patent No.. 2,l66, 596 July 18, 1959.

' CHARLES H. DASENBROOK.

It is hereby Certified that errorappears in the "printed specification of the above numbered patent requiring correction as follows: Page 2, first column, line 5, strike out the words and commevv "a depressible key ulcrumed intermediate its ends," and insert instead with the surfaces 50 and 5l so shaped and; and -that the said Letters Patent should be readwiththis cor- I'ection therein that the same may conform to the record of the case in the Patent Office.1

Signed and sealed this 5th day of September, A. D. 1959;

.l Henry Van Arsdale, (Seal) A l Acting Commissioner* of Patents.

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